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Appendix IL


The water is pumped through at A and passes by inlet-valve B,
through the filtering cartridge c, then by the outiet-valve D to
the boilers. At first the gauge E registers boiler pressure, but as
the filtering cloth on grid c becomes charged with grease, the
pressure rises, and, when-some 2olbs. higher than boiler pressure,
valves B and D are closed and bye-pass F opened, permitting the
removal of the grid to apply a new cloth.

Feed-water Heaters are contrivances for saving waste heat, by
giving it to the feed water on its way to the boiler. There are
three ways of doing this : (i) by intercepting some of the heat of
the furnace gases when leaving tbe boiler, (2) by letting the feed
pass through a vessel jacketed with exhaust steam, and (3) by
a similar use of live steam. The first apparatus, called an


economise^ is shewn in Fig. 866 standing in the flue between
boiler and chimney, The feed-water enters at A, rises simul-
taneously in pipes BB, and leaves at c on its way to the boiler
feed-valve, while the hot gases pass in the contrary direction,
D to E. There being a large accumulation of soot, the scrapers
F F, Mr. Green's invention, are used from time to time, and the
debris is dropped into chamber G. Fig. 867 is an Exhaust-steam
Feed-heater, the water entering at A and passing through the tubes,
then leaving at B for the boiler; while simultaneously the exhaust
steam travels by c to D, surrounding the tubes. Live-steam feed-
heaters have no advantage in theory, but in practice they save